Split Phase Motors (Machines)

Front 1

explain the reason for skewing the rotor bars relative to the slots on the core?

Back 1

run smoother quiter, reduce vibration

Front 2

at approx what percentage of full-load speed of the centrifugal switch contacts to open?

Back 2

75%

Front 3

state the purpose of end bells and bearings

Back 3

end bells house the bearings that allow the rotor to run freely within the stator. together they keep the rotor aligned with the stator and provide an enclosure for the motor.

Front 4

describe the constructional difference between main and auxiliary windings.

Back 4

-main(run) = heavy gauge wire, low ohms, deeper in core

-auxillary (start)= smaller gauge wire, higher ohm, closer to pole face

Front 5

flux produced by a winding is...

A) in phase with the voltage applied to coil

B) in phase with the current flowing through the coil

Back 5

B) in phase with the current flowing through the coil

Front 6

what is the physical displacement between the main and auxiliary windings in a two pole split-phase motor?

Back 6

90 degrees

Front 7

how does a magnetic pole move

Back 7

from a auxiliary(start) winding to a main(run) winding in the stator

Front 8

how is the direction of rotation reversed in a split-phase motor?

Back 8

reverse leads through auxiliary (start) winding

Front 9

why does a standard split phase motor (without a capacitor) have a low starting torque compare to a capacitor-start, split-phase motor?

Back 9

no phase displacement

Front 10

which type of split-phase motor combines good starting torque with good overload capacity?

Back 10

capacitor-start / capacitor-run

Front 11

which type of split split-phasemotor operates at synchronous speed?

Back 11

reluctance motor

Front 12

what modification is made to the rotor in the reluctance motor ?

Back 12

cut out parts of rotor, makes (salient poles)

Front 13

split phase motor, at approx what percentage of rated speed does the centrifugal switch open

Back 13

75%

Front 14

in a dual-capacitor type split-phase motor, which capacitor is capacitance is larger?

Back 14

start capacitor

Front 15

what is the most important maintenance task the should be performed on any motor?

Back 15

cleanliness

Front 16

four possible reasons that a split-phase motor might fail to start?

Back 16

-overload

-fuse blown

-open/short circuit

-open in windings

Front 17

four possible cause of excessive sparking at the commutator of a universal motor

Back 17

-high mica

-brush vibration

-not enough brush pressure

-to much load

Front 18

what should a proper film on a commutator look like

Back 18

dark brown

Front 19

three constructional between an ac series and a dc series motor

Back 19

-pole cores have lamination

-field windings in ac motors have fewer turns

-high resistance leads

Front 20

stat relationship between load and speed for series motor

Back 20

speed decreases when load is added to the circuit

Front 21

how does the rotor part of the series motor receive its energy

Back 21

brushes and commutator

Front 22

how is the direction of rotation reversed in a series motor

Back 22

interchange any armature leads

Front 23

what may happen if a large series motor is operated with no load connected ?

Back 23

motor goes to run away

Front 24

what two variables affect the counter emf generated in the armature?

Back 24

-speed

-strength of magnetic field

Front 25

what two variable affect the torque developed by the rotor of the series motor?

Back 25

-current through armature

-magnetic field

Front 26

will an ac series motor operate on DC?

Back 26

yes

Front 27

why dos the direction of rotations not change each time the alternating current changes direction

Back 27

both polaritys change, field and current through the armature

Front 28

why are the stator and rotor cores of the universal motor laminated?

Back 28

reduce eddy currents

Front 29

what are two types of windings in the stator of the shaded-pole motor?

Back 29

-exciter winding

-shading coil

Front 30

how do the two stator windings receive their energy from the source?

Back 30

-shading coil = induction

-exciter coil=conduction

Front 31

in what direction does the field move across the pole face in a shaded- pole motor?

Back 31

unshaded to shaded

Front 32

how is the direction of rotation of a shaded-pole face motor revered?

Back 32

by removing the stator and rotations the opposite way

Front 33

is the starting torque of a shaded-pole motor high or low compared to a split-phase motor?

Back 33

low

Front 34

at what speed does the rotor of hysteresis motor rotate

Back 34

synchronous speed

Front 35

from what type of steel is the rotor of hysteresis motor rotor made from?

Back 35

hardened steel ( reluctance to change polarity)